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Full-Text Articles in Life Sciences
Biodiversity And Ecosystem Function: The Consumer Connection, J. Emmett Duffy
Biodiversity And Ecosystem Function: The Consumer Connection, J. Emmett Duffy
VIMS Articles
Proposed links between biodiversity and ecosystem processes have generated intense interest and controversy in recent years. With few exceptions, however, empirical studies have focused on grassland plants and laboratory aquatic microbial systems, whereas there has been little attention to how changing animal diversity may influence ecosystem processes. Meanwhile, a separate research tradition has demonstrated strong top‐down forcing in many systems, but has considered the role of diversity in these processes only tangentially. Integration of these research directions is necessary for more complete understanding in both areas. Several considerations suggest that changing diversity in multi‐level food webs can have important ecosystem …
Long-Distance Dispersal Potential In A Marine Macrophyte, Mc Harwell, R J. Orth
Long-Distance Dispersal Potential In A Marine Macrophyte, Mc Harwell, R J. Orth
VIMS Articles
Plant populations have long been noted to migrate faster than predicted based on their life history and seed dispersal characteristics (i.e., Reid's paradox of rapid plant migration). Although precise mechanisms to account for such phenomena are not fully known for all plant species, a combination of theoretical and empirically driven mechanisms often resolves this paradox. Here, we couple a series of direct and indirect field and laboratory exercises on one marine macrophyte, Zostera marina L. (eelgrass), to measured distances between new patches and established beds in order to elucidate the longdistance dispersal and colonization potential of this marine seagrass. Detached, …
A Perspective On Two Decades Of Policies And Regulations Influencing The Protection And Restoration Of Submerged Aquatic Vegetation In Chesapeake Bay, Usa, R J. Orth, Ra Batiuk, Pw Bergstrom, Ken Moore
A Perspective On Two Decades Of Policies And Regulations Influencing The Protection And Restoration Of Submerged Aquatic Vegetation In Chesapeake Bay, Usa, R J. Orth, Ra Batiuk, Pw Bergstrom, Ken Moore
VIMS Articles
Seagrasses along with many other species of freshwater rooted submerged macrophytes in Chesapeake Bay (collectively called SAV) underwent serious declines in population abundances in the 1970s and have not as yet rebounded to previous levels. Cooperative efforts by scientists, politicians, federal and state resource managers, and the general public have developed policies and plans to protect, preserve and enhance SAV populations of Chesapeake Bay. These include the Chesapeake Bay Agreements (1983, 1987, 1992, 1993, 2000), an SAV Management Policy and Implementation Plan for Chesapeake Bay and Tidal Tributaries (1989 and 1990), Chesapeake Bay Blue Crab Fishery Management Plan (1997), as …
The Magnitude Of Spring Bacterial Production In The North Atlantic Ocean, Hw Ducklow, Dl Kirchman, Tr Anderson
The Magnitude Of Spring Bacterial Production In The North Atlantic Ocean, Hw Ducklow, Dl Kirchman, Tr Anderson
VIMS Articles
Dissolved organic carbon (DOC), a major reservoir in the ocean carbon cycle, is produced by a profusion of plankton sources and processes but is consumed mainly by bacterioplankton. Thus bacterial metabolism regulates the entry of DOC into the longer scale global carbon cycle. Bacterial production (BP) is the routinely measured quantity for evaluating the roles of bacteria in carbon cycling. However BP cannot be measured directly and instead is estimated from related metabolic processes requiring the use of poorly constrained conversion factors. BP and thus the total carbon utilization, are potentially uncertain by a factor of two or more. In …
Relative Strengths Of Competition For Space And Food In A Sessile Filter Feeder, David P. Lohse
Relative Strengths Of Competition For Space And Food In A Sessile Filter Feeder, David P. Lohse
VIMS Articles
Previous workers have demonstrated that sessile filter feeders compete for food and space, but little is known about the relative strengths of these two processes. To determine this, the density and position of barnacles (Balanus improvisus) in a unidirectional current were manipulated to alter the amount of competition for space and food, respectively. Results indicated that competition for space significantly reduced growth, and marginally reduced survivorship. Competition for food was also detected, but only among uncrowded individuals; thus, it appears to be the weaker of the two interactions. However, under crowded conditions, downstream individuals actually grew more than those upstream. …
The Microbial And Metazoan Community Associated With Colonies Of Trichodesmium Spp.: A Quantitative Survey, Cc Sheridan, Deborah K. Steinberg, Gw Kling
The Microbial And Metazoan Community Associated With Colonies Of Trichodesmium Spp.: A Quantitative Survey, Cc Sheridan, Deborah K. Steinberg, Gw Kling
VIMS Articles
Association with resource-rich particles may benefit a number of planktonic species in oligotriphic, open-ocean regimes. This study examined communities of microbes and Zooplankton associated with colonies of the cyanobacterium Trichodesmium spp. in the Sargasso Sea. Trichodesmium colonies and seawater controls were collected near Bermuda using SCUBA during September 1995, and June, July and August 1996. Organisms associated with the colonies and those in the surrounding seawater were enumerated using light and fluorescence microscopy. We found that 85% of the Trichodesmium puff and tuft colonies examined harbored associated organisms. Associated organisms included bacteria (rod and coccoid),fungi, pennate diatoms, centric diatoms, heterotrophic …
Widespread Distribution In Polar Oceans Of A 16s Rrna Gene Sequence With Affinity To Nitrosospira-Like Ammonia-Oxidizing Bacteria, Jt Hollibaugh, Hw Ducklow, N Bano
Widespread Distribution In Polar Oceans Of A 16s Rrna Gene Sequence With Affinity To Nitrosospira-Like Ammonia-Oxidizing Bacteria, Jt Hollibaugh, Hw Ducklow, N Bano
VIMS Articles
We analyzed the phylogenetic compositions of ammonia-oxidizing bacteria of the beta subclass of Proteobacteria from 42 Southern Ocean samples. We found a Nitrosospira-like 16S rRNA gene sequence in all 20 samples that yielded PCR products (8 of 30 samples from the Ross Sea and 12 of 12 samples from the Palmer Peninsula). We also found this sequence in Arctic Ocean samples, indicating a transpolar, if not global, distribution; however, slight differences between Arctic and Antarctic sequences may be evidence of polar endemism.
Estimating The Spatial Extent Of Bottom-Water Hypoxia And Habitat Degradation In A Shallow Estuary, Cp Buzzelli, Ra Luettich, Sp Powers, Ch Peterson, Je Mcninch, Jl Pinckney, Hw Paerl
Estimating The Spatial Extent Of Bottom-Water Hypoxia And Habitat Degradation In A Shallow Estuary, Cp Buzzelli, Ra Luettich, Sp Powers, Ch Peterson, Je Mcninch, Jl Pinckney, Hw Paerl
VIMS Articles
Bottom-water hypoxia (less than or equal to2 mg l(-1) dissolved oxygen [DO]) greatly modifies the benthic habitat of estuaries, depending upon spatial extent, duration, and frequency. Bottom-water hypoxia often develops under conditions of density stratification, which inhibits vertical mixing, and warm temperatures, which enhance biological oxygen demand. Long-term, mid-channel data from the Neuse River Estuary in North Carolina permitted evaluation of how stratification and temperature combined to affect DO concentrations at the bottom. Salinity stratification (AS) and water temperature (T) explained respectively 30 and 23 % of the variance in bottom-water DO concentrations. The amount of salinity stratification required to …
Hybridization Of Tetraploid And Diploid Crassostrea Gigas (Thunberg) With Diploid C-Ariakensis (Fujita), H Que, Standish K. Allen Jr.
Hybridization Of Tetraploid And Diploid Crassostrea Gigas (Thunberg) With Diploid C-Ariakensis (Fujita), H Que, Standish K. Allen Jr.
VIMS Articles
Three replicates of hybrid crosses of tetraploid and diploid C gigas (Thunberg) with diploid C ariakensis (Fujita) were produced with controls. Larval survival and growth were documented. Cytological events were also monitored in oocytes from hybrid crosses following insemination. Among the four types of hybrid crosses, diploid C. gigas (female) x diploid C. ariakensis (male) (GA) was the most successful. Survival of GA was about the same as that of controls in two of three replications, although its growth rate was 25-30% lower. Crosses of tetraploid C. gigas (female) and diploid C. ariakensis (male) (GGA) had poor yield at day …
Predation On Seeds Of The Seagrass Posidonia Australis In Western Australia, R J. Orth, Kl Heck, Dj Tunbridge
Predation On Seeds Of The Seagrass Posidonia Australis In Western Australia, R J. Orth, Kl Heck, Dj Tunbridge
VIMS Articles
Despite much evidence that predation governs seed abundance, and ultimately seedling and adult plant distribution and abundance in terrestrial ecosystems, there is a dearth of information from seagrass dominated ecosystems. We report here on the first study to examine predation rates from seeds of Posidonia australis measured during field tethering experiments at 5 locations in Western Australia. Seeds that were recently dehisced from ripe fruits and at a similar stage of development were tethered in seagrass and adjacent unvegetated sand for 24 h and then assessed for damage. Seed predation was noted at all sites and ranged from partially to …
Evidence Of Countergradient Variation In The Growth Of An Intertidal Snail In Response To Water Velocity, Gc Trussell
Evidence Of Countergradient Variation In The Growth Of An Intertidal Snail In Response To Water Velocity, Gc Trussell
VIMS Articles
Growth rates in rocky intertidal snails can vary considerably across wave exposure gradients, and have both plastic and genetic bases. However, little is known regarding whether genetic and environmental influences on variation in growth act in the same (cogradient) or in an opposing (countergradient) direction. Determining how genetic and environmental influences on growth covary with one another may improve our understanding of how habitat-specific variation in growth emerges. This study utilized laboratory flumes to examine the effects of high and low water velocities on the growth of intertidal snails Littorina obtusata from a wave-exposed and a sheltered shore. Both flow …
Active Transport Of Particulate Organic Carbon And Nitrogen By Vertically Migrating Zooplankton In The Sargasso Sea, A Schnetzer, Deborah K. Steinberg
Active Transport Of Particulate Organic Carbon And Nitrogen By Vertically Migrating Zooplankton In The Sargasso Sea, A Schnetzer, Deborah K. Steinberg
VIMS Articles
Diel vertically migrating zooplankton can contribute significantly to dissolved carbon and nutrient export by respiring and excreting surface-ingested particulate organic matter below the mixed layer. Active export of particulate organic carbon (POC) and particulate organic nitrogen (PON) due to defecation at depth has rarely been considered in export budgets. We measured the gut passage time (GPT) of common migrant species at the Bermuda Atlantic Time-series Study (BATS) site, using the gut fluorescence method, to determine whether GPT is slow enough to allow active export of POC and PON to depth. Mean GPT for the copepods Pleuromamma xiphias and Euchirella messinensis …
Habitat Quality And Prey Size As Determinants Of Survival In Post-Larval And Early Juvenile Instars Of The Blue Crab Callinectes Sapidus, R J. Orth, J Van Montfrans
Habitat Quality And Prey Size As Determinants Of Survival In Post-Larval And Early Juvenile Instars Of The Blue Crab Callinectes Sapidus, R J. Orth, J Van Montfrans
VIMS Articles
Habitat structure and prey size are important determinants in the outcome of predator-prey interactions. We investigated the role of simulated habitat type and density (simulated Zostera marina [hereafter referred to as 'Zostera']: 500 and 1500 shoots m(-2), and simulated Spartina alterniflora [hereafter referred to as 'Spartina']: 97 and 291 shoots m(-2)) in mediating predator-prey interactions. Proportional survival during predation by the piscene predator Fundulus heteroclitus on 2 successive life-history stages (post-larvae and first juvenile instars) of the blue crab Callinectes sapidus (Rathbun), was quantified under laboratory conditions that closely approximated field conditions. We also examined the effects of juvenile crab …
Ecosystem Modeling Analysis Of Size-Structured Phytoplankton Dynamics In The York River Estuary, Virginia (Usa). I. Development Of A Plankton Ecosystem Model With Explicit Feedback Controls And Hydrodynamics, Y Sin, Rl Wetzel
VIMS Articles
An ecosystem simulation model was developed to investigate potential mechanisms controlling the size-structured phytoplankton and nutrient dynamics in the mesohaline zone of the York River estuary. The model included 12 state variables in a unit volume (m(3)) describing the distribution of carbon and nutrients (nitrogen, phosphorus) in the surface mixed layer. General size-scale relationships and density-dependent feedback control terms were used in the ecosystem model. Forcing functions included incident solar radiation, water temperature, wind stress, river flow and tide, which include advective transport and turbulent mixing. Advective transport and turbulent mixing were incorporated into the model explicitly without coupling to …
Ecosystem Modeling Analysis Of Size-Structured Phytoplankton Dynamics In The York River Estuary, Virginia (Usa). Ii. Use Of A Plankton Ecosystem Model For Investigating Controlling Factors On Phytoplankton And Nutrient Dynamics, Y Sin, Rl Wetzel
VIMS Articles
An ecosystem simulation model was used to investigate potential mechanisms controlling the size-structured phytoplankton and nutrient dynamics in the mesohaline zone of the York River estuary, The York River ecosystem model (Sin & Wetzel 2001, Mar Ecol Prog Ser 228:75-90)was calibrated and validated based on field observations and laboratory measurements prior to the exercises reported here. Analyses of model sensitivity to state variable changes and parameter variations were performed to examine hypotheses proposed from previous studies regarding controls on phytoplankton and nutrient dynamics in the York River estuary. The model results supported the general view that phytoplankton dynamics may be …
Total Cover And Cover Quality: Predicted And Actual Effects On A Predator's Foraging Success, A Bartholomew
Total Cover And Cover Quality: Predicted And Actual Effects On A Predator's Foraging Success, A Bartholomew
VIMS Articles
I tested the importance of both total cover and cover quality to the foraging ability of large Fundulus heteroclitus fish in tanks. Total cover was measured as the combined areas of all the individual structures, viewed as shadows. I divided total cover by the bottom area of the tank to form C-t/A(t), an index that measures the total amount of structure available in a given area for prey to hide behind. Cover quality was measured as the width of each individual structure divided by the width of the individual prey organism (C-w/P-w). This index measures how visible a prey organism …
Photo Synthesis/Irradiance Relationships In The Ross Sea, Antarctica, And Their Control By Phytoplankton Assemblage Composition And Environmental Factors, C. M. Van Hilst, Walker O. Smith Jr.
Photo Synthesis/Irradiance Relationships In The Ross Sea, Antarctica, And Their Control By Phytoplankton Assemblage Composition And Environmental Factors, C. M. Van Hilst, Walker O. Smith Jr.
VIMS Articles
The photosynthetic parameters of natural phytoplankton assemblages from the Ross Sea, Antarctica, as well as unialgal cultures of the diatom Pseudonitzschia sp. and the colonial haptophyte Phaeocystis antarctica were investigated to determine if differential responses to irradiance could explain the distribution of phytoplankton in the Ross Sea. Field assemblages had photosynthetic responses that suggested acclimation to low irradiance levels, and the initial rate of photosynthesis per unit chlorophyll (a) and the theoretical maximum rate of production (p(max)(B)) averaged 0,083 mg C (mg chl a)(-1) h(-1) (mumol m(-2) s(-1))(-1) and 2,40 mg C (mg chl a)(-1) h(-1), respectively. An increase in …